Doctors have long known that Alzheimer’s disease spreads through the brain over many years, but exactly how this happens has remained a mystery.
The illness gradually destroys brain cells, causing memory loss, confusion and changes in behaviour. As more areas of the brain become affected, everyday activities become increasingly difficult.
Researchers from University of Utah Health believe they have identified one of the mechanisms behind this spread. Their study, published in Cell, focused on a protein called Arc that normally helps brain cells exchange information during learning and memory.
Under healthy conditions, Arc is beneficial. It travels between neurons inside tiny membrane-covered packages called extracellular vesicles. These small sacs allow brain cells to send important signals to each other as part of normal brain function.
The scientists discovered that toxic Tau proteins appear to hijack this natural transport system. Instead of carrying only healthy signals, the vesicles can also carry harmful Tau from one diseased neuron into a healthy one. Once inside, the abnormal Tau encourages healthy Tau proteins to form damaging clumps.
To test this idea, the researchers studied mice that developed Alzheimer’s-like disease. Some mice produced Arc normally, while others lacked the protein. The difference between the two groups was striking.
Mice without Arc had very little Tau inside their extracellular vesicles, and the disease spread much less effectively between neighbouring neurons. This showed that Arc is closely involved in moving harmful Tau through the brain.
Even so, the study revealed an unexpected complication. Arc also helps damaged neurons survive by allowing them to release some of their toxic Tau. When Arc was missing, more Tau stayed trapped inside sick neurons, causing those cells to die faster.
These findings suggest that completely blocking Arc may not be the best treatment strategy. A better option may be to prevent the vesicles carrying Tau from entering healthy brain cells while still allowing damaged neurons to remove excess protein. Such an approach could slow the disease without creating additional problems.
The researchers also found evidence of Arc and Tau together in human brain tissue, raising the possibility that the same process occurs in people. However, they emphasise that this evidence is still preliminary and that clinical treatments remain a long way off.
This research opens an exciting new direction in Alzheimer’s science by focusing on how the disease spreads rather than how it begins. The study combines detailed laboratory work with animal experiments, making the findings scientifically valuable.
Nevertheless, because the research has not yet been tested in patients, it should be viewed as an important early discovery rather than a proven treatment. Future human studies will determine whether targeting these tiny vesicles can help slow Alzheimer’s disease.
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Source: University of Utah Health.
